公开(公告)号：US11236406B2

公开(公告)日：2022-02-01

申请号：US16620615

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Takashi Kobayashi ,  Yoshimasa Funakawa ,  Seiji Nakajima

IPC: C21D9/46 ,  B21D22/02 ,  B32B15/01 ,  C21D1/18 ,  C21D6/00 ,  C21D8/02 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/10 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C23C30/00

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing as high as TS: 1780 MPa or more, and excellent indentation peeling strength at projection welds by properly adjusting its chemical composition and its microstructure such that a prior austenite average grain size is 7 μm or less within a range of 50 μm or less in a thickness direction from a surface of the member, a volume fraction of martensite is 90% or more, and an average intergrain distance of Nb and Ti carbonitrides having a grain size of less than 0.10 μm within a depth range of 20 μm to 100 μm in the thickness direction from the surface of the member is 5 μm or less.

公开(公告)号：US11111558B2

公开(公告)日：2021-09-07

申请号：US16619814

申请日：2018-03-30

Applicant: JFE STEEL CORPORATION

Inventor： Katsutoshi Takashima ,  Takashi Kobayashi ,  Yoshimasa Funakawa ,  Seiji Nakajima

IPC: B32B15/01 ,  C21D9/48 ,  C21D6/00 ,  C21D8/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/08 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/12 ,  C23C2/40

Abstract: Disclosed is a hot-pressed member that can exhibit very high tensile strength after hot pressing as high as TS: 1780 MPa or more, and excellent resistance to resistance welding cracking by properly adjusting its chemical composition and its microstructure such that a prior austenite average grain size is 7.5 μm or less, a volume fraction of martensite is 95% or more, and at least 10 Nb-based and Ti-based precipitates having a grain size of less than 0.10 μm are present on average per 100 μm2 of a cross section parallel to a thickness direction of the member within a range of 100 μm or less in the thickness direction from the surface of the member, and such that a B concentration in prior austenite grain boundaries is at least 3.0 times a B concentration at a position 5 nm away from the grain boundaries.

公开(公告)号：US20210180151A1

公开(公告)日：2021-06-17

申请号：US17178518

申请日：2021-02-18

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  C22C38/58 ,  C22C38/38 ,  C22C38/14 ,  C22C38/12 ,  C22C38/04 ,  C21D8/02 ,  C22C38/16 ,  C22C38/46 ,  C22C38/40 ,  C21D6/00 ,  C22C38/44 ,  C22C38/42 ,  C22C38/28 ,  C22C38/48 ,  C22C38/18 ,  C22C38/54 ,  C22C38/08 ,  C23C2/12 ,  B32B15/01 ,  B32B15/04 ,  C23C28/02 ,  C23C2/02 ,  C23C30/00 ,  B32B15/18 ,  C23C2/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/06 ,  C22C38/20 ,  C22C38/22 ,  C22C38/24 ,  C22C38/26 ,  C22C38/32 ,  C22C38/50 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A method for producing a hot-rolled steel sheet, a method for producing a cold-rolled full-hard steel sheet, and a method for producing a heat-treated sheet are provided herein. The methods comprising hot rolling a steel material of a composition comprising, in mass %, C: 0.05 to 0.12%, Si: 0.80% or less, Mn: 1.30 to 2.10%, P: 0.001 to 0.050%, S: 0.005% or less, Al: 0.01 to 0.10%, N: 0.010% or less, one or more selected from Cr in an amount of 0.05 to 0.50%, and Mo in an amount of 0.05 to 0.50%, one or more selected from Ti in an amount of 0.01 to 0.10%, Nb in an amount of 0.01 to 0.10%, and V in an amount of 0.01 to 0.10%, and the balance Fe and unavoidable impurities.

公开(公告)号：US10946470B2

公开(公告)日：2021-03-16

申请号：US16062407

申请日：2016-12-13

Applicant: JFE STEEL CORPORATION

Inventor： Chikaumi Sawanishi ,  Koichi Taniguchi ,  Katsutoshi Takashima ,  Hiroshi Matsuda ,  Rinsei Ikeda

IPC: B23K11/11 ,  B23K11/16

Abstract: Provided is a resistance spot welding method that inhibits, in accordance with the degree of axis misalignment between electrodes, the occurrence of cracking in a weld regardless of the steel grade. In resistance spot welding methods according to the present invention, H (ms) is an electrode force retaining time after completion of current passage, D (mm) is an amount of axis misalignment between the electrodes, t (mm) is a total sum of sheet thicknesses of a plurality of overlapping steel sheets, T (MPa) is a tensile strength of a steel sheet having a highest tensile strength among the plurality of steel sheets, F (N) is an electrode force, and d (mm) is a tip diameter of one electrode of the pair of electrodes that has a smaller tip diameter. The electrode force retaining time H is specified to be a predetermined value or greater.

公开(公告)号：US10920293B2

公开(公告)日：2021-02-16

申请号：US16089096

申请日：2017-03-21

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Yoshimasa Funakawa

IPC: C21D9/46 ,  C21D8/02 ,  C23C2/06 ,  C22C38/06 ,  C23C2/28 ,  C22C38/60 ,  C22C38/58 ,  C21D1/74 ,  C22C18/00 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/18 ,  C23C2/02 ,  C23C2/40 ,  C22C18/04

Abstract: Provided herein is a plated steel having high strength with excellent elongation, excellent hole expansibility, and excellent material uniformity, and a method for producing such a plated steel. The steel sheet provided herein has a specific composition, and a steel structure that contains ferrite as a primary phase, and 2 to 12% of perlite, and 3% or less of martensite by volume, and in which the remainder is a low-temperature occurring phase. The ferrite has an average crystal grain diameter of 25 μm or less. The perlite has an average crystal grain diameter of 5 μm or less. The martensite has an average crystal grain diameter of 1.5 μm or less. The perlite has a mean free path of 5.5 μm or more. The steel sheet has a tensile strength of 440 MPa or more.

公开(公告)号：US20170107591A1

公开(公告)日：2017-04-20

申请号：US15128516

申请日：2015-03-17

Applicant: JFE Steel Corporation

Inventor： Katsutoshi Takashima ,  Kohei Hasegawa

IPC: C21D9/46 ,  C22C38/28 ,  C22C38/16 ,  C22C38/14 ,  C22C38/12 ,  C23G1/00 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C22C38/38 ,  C22C38/08

CPC classification number: C21D9/46 ,  C21D1/25 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0263 ,  C21D8/0273 ,  C21D8/0278 ,  C21D8/0473 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/005 ,  C21D2211/008 ,  C22C38/001 ,  C22C38/002 ,  C22C38/005 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/38 ,  C22C38/58 ,  C23G1/00

Abstract: A high-yield-ratio, high-strength cold-rolled steel sheet has a composition containing, in terms of % by mass, C: 0.13% to 0.25%, Si: 1.2% to 2.2%, Mn: 2.0% to 3.2%, P: 0.08% or less, S: 0.005% or less, Al: 0.01% to 0.08%, N: 0.008% or less, Ti: 0.055% to 0.130%, and the balance being Fe and unavoidable impurities. The steel sheet has a microstructure that contains 2% to 15% of ferrite having an average crystal grain diameter of 2 um or less in terms of volume fraction, 5 to 20% of retained austenite having an average crystal grain diameter of 0.3 to 2.0 μm in terms of volume fraction, 10% or less (including 0%) of martensite having an average grain diameter of 2 μm or less in terms of volume fraction, and the balance being bainite and tempered martensite, and the bainite and the tempered martensite having an average crystal grain diameter of 5 μm or less.

公开(公告)号：US12276028B2

公开(公告)日：2025-04-15

申请号：US18251422

申请日：2021-11-05

Applicant: JFE STEEL CORPORATION

Inventor： Shunsuke Yamamoto ,  Katsutoshi Takashima ,  Mai Aoyama ,  Yusuke Okumura ,  Tomomi Kanazawa ,  Katsuya Hoshino ,  Hiroshi Matsuda ,  Ei Okumura ,  Yoichi Makimizu ,  Masaki Koba

IPC: C23C2/02 ,  C21D1/74 ,  C21D6/00 ,  C21D8/02 ,  C21D9/46 ,  C22C33/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/08 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C23C2/28 ,  C23C2/40 ,  C23C28/00 ,  C23F17/00 ,  C25D3/56 ,  C25D5/36 ,  C25D5/48 ,  B23K11/11 ,  B23K11/16 ,  B23K101/34

Abstract: Provided is a galvanized steel sheet with excellent resistance to cracking in resistance welding at a welded portion, even if crystal orientations of an Fe-based electroplating layer and a cold-rolled steel sheet are integrated at a high ratio at the interface between the Fe-based electroplating layer and the cold-rolled steel sheet. The galvanized steel sheet has a Si-containing cold-rolled steel sheet containing Si in an amount of 0.1 mass % to 3.0 mass %; an Fe-based electroplating layer formed on at least one surface of the Si-containing cold-rolled steel sheet with a coating weight per surface of more than 20.0 g/m2, and a galvanized layer formed on the Fe-based electroplating layer, where crystal orientations of the Fe-based electroplating layer and the Si-containing cold-rolled steel sheet are integrated at a ratio of more than 50 % at the interface between the Fe-based electroplating layer and the Si-containing cold-rolled steel sheet.

公开(公告)号：US12241137B2

公开(公告)日：2025-03-04

申请号：US17420216

申请日：2019-12-23

Applicant: JFE Steel Corporation

Inventor： Yoshie Obata ,  Katsutoshi Takashima ,  Takeshi Yokota

IPC: C21D9/46 ,  C21D6/00 ,  C21D8/02 ,  C22C18/04 ,  C22C38/00 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/12 ,  C22C38/14 ,  C22C38/16 ,  C22C38/26 ,  C22C38/28 ,  C22C38/32 ,  C22C38/38 ,  C22C38/60 ,  C23C2/06 ,  C23C2/28 ,  C23C2/40

Abstract: A high-strength cold rolled steel sheet has a specific composition and a steel structure that is, by volume %, 10%-70% ferrite, 1%-10% retained austenite, 10%-60% bainite, and 2%-50% martensite, the average crystal grain size of the ferrite being no more than 6.0 μm, the average crystal grain size of the retained austenite being no more than 4.0 μm, the average crystal grain size of the bainite being no more than 6.0 μm, and the average crystal grain size of the martensite being no more than 4.0 μm. The concentration ratio of the average concentration of Si to a depth of 10 μm from the surface of the high-strength cold-rolled steel sheet to the average concentration of Si throughout the high-strength cold-rolled steel sheet is, by mass ratio, greater than 1.00 but less than 1.30.

公开(公告)号：US20240271256A1

公开(公告)日：2024-08-15

申请号：US18289928

申请日：2022-05-17

Applicant: JFE Steel Corporation

Inventor： Yoichi Makimizu ,  Shunsuke Yamamoto ,  Yusuke Okumura ,  Katsuya Hoshino ,  Ei Okumura ,  Katsutoshi Takashima

IPC: C22C38/04 ,  C21D9/46 ,  C22C38/02 ,  C22C38/06 ,  C23C2/26 ,  C23C28/02

CPC classification number: C22C38/04 ,  C21D9/46 ,  C22C38/02 ,  C22C38/06 ,  C23C2/26 ,  C23C28/025

Abstract: A base steel sheet containing Si in an amount of 0.50 to 3.00 mass % is subjected to an Fe-based electroplating treatment using an Fe-based electroplating solution containing Fe ions and transition metal ions other than the Fe ions to form an Fe-based electroplated layer, and then to an annealing treatment. In the Fe-based electroplating solution, a content of the Fe ions is 1.0 mass % or more and a content of the transition metal ions is 10 to 1000 mass ppm. A coating amount of the Fe-based electroplated layer per one surface of the base steel sheet is 1.0 g/m2 or more. Thus, a steel sheet having high strength and excellent resistance to resistance-weld cracking of a welded portion is obtained.

公开(公告)号：US20240110264A1

公开(公告)日：2024-04-04

申请号：US18285524

申请日：2022-03-02

Applicant: JFE Steel Corporation

Inventor： Lingling Yang ,  Yuki Toji ,  Ryohei Morimoto ,  Katsutoshi Takashima

IPC: C22C38/04 ,  C21D8/02 ,  C22C38/02 ,  C22C38/06 ,  C23C2/02 ,  C23C2/06

CPC classification number: C22C38/04 ,  C21D8/0205 ,  C21D8/0226 ,  C21D8/0236 ,  C21D8/0273 ,  C22C38/02 ,  C22C38/06 ,  C23C2/0224 ,  C23C2/06 ,  C21D2211/001 ,  C21D2211/002 ,  C21D2211/008

Abstract: A high-strength cold-rolled steel sheet has a chemical composition containing C: 0.150 to 0.350 mass %, Si: 0.80 to 3.00 mass %, Mn: 1.50 to 3.50 mass %, P: 0.100 mass % or less, S: 0.0200 mass % or less, Al: 0.100 mass % or less, N: 0.0100 mass % or less, and O: 0.0100 mass % or less, with a remaining part consisting of Fe and impurities. The amount of diffusible hydrogen is 0.50 mass ppm or less, the area ratio of tempered martensite and bainite is 55 to 95%, the area ratio of retained austenite is 5 to 30%, a prior austenite grain has an average circle equivalent diameter of 15.0 μm or less, and the ratio b/a is 0.80 or less, where a circumferential length of the prior austenite grain is a, and a circumferential length of a portion of the prior austenite grain having a carbon concentration of 0.6 mass % or more is b.